Most men prefer leggy and lean women, Gisele Bündchen lookalikes, right? Not necessarily. In fact, the body type that a man finds attractive can change depending on his environment and circumstances, a new study finds: when under stress, for instance, men prefer heavier women.

The study, published in the journal PLoS ONE, reports that when men were placed in stressful situations, then asked to rate the attractiveness of women of varying body sizes, they tended to prefer beefier frames, compared with unstressed men whose tastes skewed thinner.

“This suggests that our body size preferences are not innate, but are flexible,” said study co-author Martin Tovée of Newcastle University in the U.K., in an email, noting that they may be influenced by our particular environment and resources.

The findings fall in line with evolutionary theories that suggest when resources are scarce or unpredictable, a woman’s thin physique may signal illness, frailty and the inability to reproduce. Indeed, Tovée and colleague Viren Swami of the University of Westminster in London have previously found that men under trying conditions — like extreme hunger — tend to rate heavier women as more attractive. The researchers suggest also that underlying biological mechanisms, such as blood sugar and hormone levels, are major players in how we perceive our surroundings.

“Our work in parts of Malaysia and Africa has shown that in poorer environments where resources are scarce, people prefer a heavy body in a potential partner,” said Tovée. “If you live in an environment where food is scarce, being heavier means you have fat stored up as a buffer against a potential food reduction in the future, and that you must be higher social status to afford the food in the first place. Both of these are attractive qualities in a partner in those circumstances.”

Moving from a low-resource environment to a richer one, like the U.K. or the U.S., can cause a shift in these preferences, says Tovée, and to test the theory further, the researchers recruited some male volunteers and manipulated their stress levels — a key problem for people living in poor environments.

The study examined 81 heterosexual men, about half of whom underwent the Trier Social Stress Test. In the test, the men participated in an impromptu job interview in front of four interviewers. They were asked them to “sell” themselves for five minutes, and then calculate answers to simple math problems under time pressure.

Afterward, all the study participants were shown images of 10 women with body types ranging from emaciated to obese and were asked to rank them based on their attractiveness.

The images were numbered on a scale of 1 to 10 based on the women’s body mass index (BMI), with 1 representing very thin and 10 obese. The largest body size rated attractive by the stressed-out men was 7.17, which fell in the overweight category. The largest body type deemed attractive by the unstressed control group was 6.25, which was considered normal on the BMI scale.

Overall, stressed men preferred a bigger body — their “ideal” figure was a 4.44 — than the unstressed men, who idealized a thinner body type, at 3.90. Stressed-out men not only rated heavier women as more attractive, but they also gave higher ratings to a wider range of body types overall.

“This shift suggests that stress alters what you find attractive in a potential partner, and it is another factor helping you to optimize the fit of your partner preferences to your environment,” said Tovée.

Understanding how body preferences may change or be influenced by circumstance also sheds light on the development of warped body image, the authors say. “People suffering from conditions such as anorexia nervosa have a distorted perception of body size and body ideals, and it’s important that research focus on the mechanisms underlying and influencing the perception of body size,” says Tovée.

Despite our media’s seeming reverence for size-zero models and ripped muscle men, it may help people suffering from eating disorders and other body-image problems to know that such body “ideals” are not exactly ideal after all. “The information from this article could be useful in therapy of anxiety and eating disorders,” Dr. Igor Galynker, associate chairman of the department of psychiatry and behavioral sciences at Beth Israel Medical Center, told ABC News. “The information could be an alternative to thoughts such as, ‘I am fat; no man would find me attractive.'”